The present invention relates generally to the fabrication of PC (printed circuit) boards and, more particularly, to a PC board micro hole processing method adapted to process micro holes on PC boards.
Conventional PC board micro hole processing methods include Mechanical Drilling and Laser Via. These two methods have drawbacks as outlined hereinafter:
1. Mechanical drilling:
(a) Due to technical limitation, this mechanical drilling method cannot make micro holes of diameter below 0.1 mm.
(b) Due to low hole-making speed, the micro hole processing cost is high.
(c) The drill bits used in this mechanical drilling method are expensive, and tend to be damaged during drilling, causing the micro hole processing cost to be relatively increased.
(d) Due to vibration of the power drill during drilling operation, it is difficult to control the quality of the micro holes.
2. Laser Via:
(a) Laser Via technique is applicable to make micro holes of small diameter, however due to laser energy and parameter control difficulty, the periphery of every micro hole tends to be carbonized, affecting further PTH (Plated Through Hole) procedure.
(b) Laser Via technique takes much time to make holes on the PC board, more particularly when processing micro holes on a PC board of thickness over 0.1 mm, and the expensive laser processing equipment greatly increases the micro hole processing cost.
(c) During the application of Laser Via technique, the PC board will be caused to release gaseous gases including carbon dioxide, polychlorinated biphenyl, and n-propyl bromide that will damage the ozone layer of the atmosphere and pollute the environment.
The present invention has been accomplished to provide a PC board micro hole processing method, which eliminates the aforesaid drawbacks. It is the main object of the present invention to provide a PC board micro hole processing method, which is efficient, cost-saving, and pollution-free.
To achieve the object of the present invention, the PC board micro hole processing method comprises the step of using plasma technique to etch the substrate of the PC board, and the step of using chemical etching technique to remove residual material (for example, glass fibers) left after the application of plasma technique.